ABSTRACT
Type XVIII collagen is a homotrimeric basement membrane molecule of unknown function, whose COOH-terminal NC1 domain contains endostatin (ES), a potent antiangiogenic agent. The Caenorhabditis elegans collagen XVIII homologue, cle-1, encodes three developmentally regulated protein isoforms expressed predominantly in neurons. The CLE-1 protein is found in low amounts in all basement membranes but accumulates at high levels in the nervous system. Deletion of the cle-1 NC1 domain results in viable fertile animals that display multiple cell migration and axon guidance defects. Particular defects can be rescued by ectopic expression of the NC1 domain, which is shown to be capable of forming trimers. In contrast, expression of monomeric ES does not rescue but dominantly causes cell and axon migration defects that phenocopy the NC1 deletion, suggesting that ES inhibits the promigratory activity of the NC1 domain. These results indicate that the cle-1 NC1/ES domain regulates cell and axon migrations in C. elegans.
Subject(s)
Axons/physiology , Caenorhabditis elegans/physiology , Cell Movement , Collagen/metabolism , Neurons/physiology , Peptide Fragments/metabolism , Protein Structure, Tertiary , Amino Acid Sequence , Angiogenesis Inhibitors/genetics , Angiogenesis Inhibitors/metabolism , Animals , Animals, Genetically Modified , Blotting, Western , Caenorhabditis elegans/cytology , Caenorhabditis elegans/genetics , Collagen/chemistry , Collagen/genetics , Collagen Type XVIII , Endostatins , Genes, Reporter/genetics , Male , Microscopy, Fluorescence , Molecular Sequence Data , Peptide Fragments/chemistry , Peptide Fragments/genetics , Protein Isoforms , RNA/antagonists & inhibitors , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Sequence AlignmentABSTRACT
Collagen XVIII (c18) is a triple helical endothelial/epithelial basement membrane protein whose noncollagenous (NC)1 region trimerizes a COOH-terminal endostatin (ES) domain conserved in vertebrates, Caenorhabditis elegans and Drosophila. Here, the c18 NC1 domain functioned as a motility-inducing factor regulating the extracellular matrix (ECM)-dependent morphogenesis of endothelial and other cell types. This motogenic activity required ES domain oligomerization, was dependent on rac, cdc42, and mitogen-activated protein kinase, and exhibited functional distinction from the archetypal motogenic scatter factors hepatocyte growth factor and macrophage stimulatory protein. The motility-inducing and mitogen-activated protein kinase-stimulating activities of c18 NC1 were blocked by its physiologic cleavage product ES monomer, consistent with a proteolysis-dependent negative feedback mechanism. These data indicate that the collagen XVIII NC1 region encodes a motogen strictly requiring ES domain oligomerization and suggest a previously unsuspected mechanism for ECM regulation of motility and morphogenesis.
Subject(s)
Bacterial Proteins , Cell Movement/physiology , Collagen/metabolism , Endothelium, Vascular/cytology , Extracellular Matrix/physiology , Peptide Fragments/metabolism , Protein Structure, Tertiary , Angiogenesis Inhibitors/genetics , Angiogenesis Inhibitors/metabolism , Animals , Bacterial Toxins/pharmacology , Blotting, Western , Cell Movement/drug effects , Cells, Cultured , Collagen/chemistry , Collagen/genetics , Collagen Type XVIII , Cytotoxins/pharmacology , Dimerization , Endostatins , Endothelium, Vascular/drug effects , Endothelium, Vascular/growth & development , Humans , Mice , Mitogen-Activated Protein Kinases/metabolism , Morphogenesis , Peptide Fragments/chemistry , Peptide Fragments/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , cdc42 GTP-Binding Protein/genetics , cdc42 GTP-Binding Protein/metabolism , rac GTP-Binding Proteins/genetics , rac GTP-Binding Proteins/metabolism , rho GTP-Binding Proteins/metabolismABSTRACT
Papilin is an extracellular matrix glycoprotein that we have found to be involved in, (1) thin matrix layers during gastrulation, (2) matrix associated with wandering, phagocytic hemocytes, (3) basement membranes and (4) space-filling matrix during Drosophila development. Determination of its cDNA sequence led to the identification of Caenorhabditis and mammalian papilins. A distinctly conserved 'papilin cassette' of domains at the amino-end of papilins is also the carboxyl-end of the ADAMTS subgroup of secreted, matrix-associated metalloproteinases; this cassette contains one thrombospondin type 1 (TSR) domain, a specific cysteine-rich domain and several partial TSR domains. In vitro, papilin non-competitively inhibits procollagen N-proteinase, an ADAMTS metalloproteinase. Inhibiting papilin synthesis in Drosophila or Caenorhabditis causes defective cell arrangements and embryonic death. Ectopic expression of papilin in Drosophila causes lethal abnormalities in muscle, Malpighian tubule and trachea formation. We suggest that papilin influences cell rearrangements and may modulate metalloproteinases during organogenesis.
